<template>
  <div>
    <router-link
      class="header-abs"
      tag="div"
      to="/"
      v-show="showAbs"
    >
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showAbs"
      :style="opacityStyle"
    >
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>

<script>
  export default {
    name: "DetailHeader",
    data() {
      return {
        showAbs: true,
        opacityStyle:{
          opacity: 0
        }
      }
    },

    methods: {
      handleScroll () {
        // console.log(document.documentElement.scrollTop)
        const top = document.documentElement.scrollTop;
        if (top > 60) {
          let opacity = top  / 140;
          opacity = opacity > 1 ? 1: opacity;
         this.opacityStyle = {opacity};
          this.showAbs = false
        } else {
          this.showAbs = true
        }
      }
    },
    activated () {
      window.addEventListener('scroll',this.handleScroll);
    },
    // 使用window绑定的时间，要进行解绑
    // keep-alive的生命周期函数组件即将被隐藏时。
    deactivated () {
      window.removeEventListener('scroll',this.handleScroll);
    }
  }
</script>

<style scoped lang="stylus">
  @import '~styles/varibles.styl'
  .header-abs
    position absolute
    left .2rem
    top .2rem
    width .8rem
    height .8rem
    line-height .8rem
    text-align center
    border-radius .4rem
    background-color rgba(0,0,0,.8)
    .header-abs-back
      color #ffffff
      font-size .4rem

  .header-fixed
    z-index 2
    position fixed
    top 0
    left 0
    right 0
    height $headerHeight
    line-height $headerHeight
    text-align center
    color #fff
    background $bgColor
    font-size .32rem
    .header-fixed-back
      position absolute
      top 0
      left 0
      width .64rem
      text-align center
      font-size .4rem
      color #fff
</style>
